C 9°+ ] 
If lometimes we carefully attend to the operations of 
nature, we now and then make difcoveries which 
mu ft other wife have efcaped us. If we pour nitrous 
or vitriolic acid upon that ftoney fubftance, which is 
ufually called crabs-eyes, and let them remain in the 
glafs for a conftderable time perfectly ftill, we fhali 
find at the bottom of the veffel, after the terreftriat 
parts are thoroughly diftblved, a membranous fub- 
ftance or jelly, exactly in fize and figure refembling 
the crabs-eyes, and which the acid had left un- 
touched. Exaftly fuch a gelatinous mafs our author 
has obferved in ftones of the bladder, more particu- 
larly in fmall ones, after diffolving them in acids. 
If crabs-eyes are infufed in an alcaline lixivium for a 
confiderable time, we fee no change in them, which 
can be properly called a folution : about them we ob- 
ferve a certain vifcid appearance like a cloud ; if that is 
taken away, and the crabs-eyes are dried, and after- 
wards weighed, they have not only loft part of their 
weight, but are become much more friable ; which 
is a great argument that they have loft fomething. 
If afterwards thefe crabs-eyes are wafhed with warm 
water, to carry off the alcaline matter adhering to 
them, and afterwards fet to diffolve in acids, thefe 
crabs-eyes, after the folution of their terreftrial parts, 
leave nothing gelatinous behind them, as they did 
in the other experiment ; from v/hence it is plain, 
that the gelatinous f.ibftance had been extracted and 
diffolved by the alcaline lixivium. The very fame 
thing happens to the human calculus. 
It appears therefore more than probable to our au- 
thor, that lime-water and Carlfbad waters, on account 
of their alike partaking of the alcaline and calcarious 
principle, 
